Basic introduction to probability

Surprisingly the basic introduction to probability was found in a biology book!
Here is the summary:
Product Rule:
When two or more events are independent, the probability that they will occur in succession is calculated using the product rule--their individual probabilities are multiplied. Ex : probability of getting two heads in succession is 1/2 x 1/2 = 1/4

Sum Rule:
Sum Rule is applied when there are two or more different ways of obtaining the same outcome; that is, the probability tat either event A or event B will occur equals P(A) + P(B)

Source: Billogy: Te dynamic science by Peter Russell p.240

probability of taking the correct seat

100 passengers are waiting to board a flight having 100 seats. Each of them is having a ticket with a particular seat number which is same as their number in the queue. Unfortunately the first person in the queue is little crazy and he can occupy any random seat. Now, all other passengers will see if their seat is occupied by that crazy guy or not? If not, then they will be seated on their own seat numbers otherwise they will also look for a free random seat to sit on. This continues. What's the probability that the 100th person gets his own seat to sit on?

Answer:

1. Probability of the first person taking his seat = 1/2 (no its not 1/100, since there are only two chances , either he may sit in the correct place or he may not)
2. Probability of the second person taking this correct seat = 1/2
....
so even for the 100th person, it will be 1/2

probability of seeing a car

If the probability of observing a car in 30 minutes on a highway is 0.95, what is the probability of observing a car in 10 minutes

P(A intersection B) = P(A)*P(B)
so probability of observing a car in 10 mins = ³√0.95